Window regulators for a cable driven window lifter in an automotive vehicle commonly include a closed loop cable for transferring a force supplied by a motor to lift or lower a window pane. Opposing ends of the cable are secured to a cable drum and the cable is typically wound around the cable drum which is rotationally driven by the motor. The cable is also guided around upper and lower cable pulleys supported by opposing ends of a guide rail. A lifter is slidably coupled to the guide rail and attached to the cable between the upper and lower pulleys. The window pane is secured to the lifter such that the window pane is lifted or lowered by movement of the lifter along the guide rail between the upper and lower pulleys. This type of window regulator is disclosed in U.S. Pat. No. 5,047,077.
Window regulators also often incorporate means for compensating for cable slackness when the lifter is in a relaxed state; that is, not lifting or lowering the window pane. The U.S. Pat. No. 5,857,635 discloses a window regulator wherein one end of the cable is attached to a cable drum and the opposite end of the cable is attached to a conduit-like slide disposed inside the cable drum. When the cable is unloaded, a spring urges the slide rotationally about the cable drum to take up cable slackness. However, the slide does not maintain tension in the cable when the window pane is lifted or lowered by rotation of the cable drum.